Transferring NFSv4 nfs/ keys from KDC to client?

Wed Mar 19 18:36:22 EDT 2014

On Wed, 2014-03-19 at 23:16 +0100, Wendy Lin wrote:
> On 19 March 2014 14:11, steve <steve at steve-ss.com> wrote:
> > On Wed, 2014-03-19 at 13:32 +0100, Wendy Lin wrote:
> >> On 19 March 2014 09:55, steve <steve at steve-ss.com> wrote:
> >> > On Wed, 2014-03-19 at 00:09 +0100, Wendy Lin wrote:
> >> >> On 18 March 2014 23:54, steve <steve at steve-ss.com> wrote:
> >> >> > On Tue, 2014-03-18 at 23:20 +0100, Wendy Lin wrote:
> >> >> >> Asking here to make sure I got the mechanism right:
> >> >> >>
> >> >> >> I created the principal nfs/china.mytest.org at TEST1.MYTEST.ORG on the
> >> >> >> KDC machine so that NFSv4 client china.mytest.org can mount a NFSv4
> >> >> >> filesystem.
> >> >> >>
> >> >> >> How does the client china.mytest.org now get the keys?
> >> >> >
> >> >> > Hi
> >> >> > It doesn't need to. rpc.gssd can use any of the following keys:
> >> >> > <HOSTNAME>$@<REALM>
> >> >> > root/<hostname>@<REALM>
> >> >> > nfs/<hostname>@<REALM>
> >> >> > host/<hostname>@<REALM>
> >> >> > root/<anyname>@<REALM>
> >> >> > nfs/<anyname>@<REALM>
> >> >> > host/<anyname>@<REALM>
> >> >> >
> >> >> > Just make sure that your keytab has one of them. Usually it will already
> >> >> > have the CHINA$ key, so you can mount using that. The nfs server keytab
> >> >> > should have both the nfs servivce and machine keys.
> >> >> >
> >> >> > There are many misunderstandings about kerberized nfs:
> >> >> > http://linuxcostablanca.blogspot.com.es/2012/02/nfsv4-myths-and-legends.html
> >> >> > HTH
> >> >> > Steve
> >> >>
> >> >> What I did is:
> >> >> 1. Have kadmind running on the kdc
> >> >> 2. Run kadmin on the client as user root. A principal root@<REALM> exists
> >> >> 3. Use ktadd in kamin to download the keys for
> >> >> nfs/<clienthostname>@<REALM> and host/<clienthostname>@<REALM> .
> >> >>
> >> >> Still it does not work here and the mount fails:
> >> >> mount -t nfs4 test1.mytest.org:/ /mnt
> >> >> mount.nfs4: access denied by server while mounting nexentapuzzle.nrubsig.org:/
> >> >
> >> > Tell it to use Kerberos:
> >> > mount -t nfs4 test1.mytest.org:/ /mnt -osec=krb5
> >> >>
> >> >> gssd is running:
> >> >> # ps -ef | fgrep gss
> >> >> root      1403     1  0 Mar18 ?        00:00:00 /usr/sbin/rpc.svcgssd
> >> >> root      1420     1  0 Mar18 ?        00:00:00 /usr/sbin/rpc.gssd
> >> >>
> >> >> I have not a clue what I am doing wrong. Please help.
> >> >
> >> > Tell it to use Kerberos:
> >> > mount -t nfs4 test1.mytest.org:/ /mnt -osec=krb5
> >> >
> >> > If still nothing send the output of:
> >> > klist -ke
> >> > on both the client and the server?
> >>
> >> @(nfs|krb) server (hostname "test1.mytest.org"):
> >> # klist -ke /etc/krb5.keytab
> >> Keytab name: WRFILE:/etc/krb5.keytab
> >> KVNO Principal
> >> ---- --------------------------------------------------------------------------
> >>    2 nfs/test1 at TEST1.MYTEST.ORG (DES cbc mode with CRC-32)
> >>    2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (DES cbc mode with CRC-32)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
> >>    3 host/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    3 host/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    3 host/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
> >>    3 host/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
> >>    2 host/test1.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
> >>    2 host/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
> >>    2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
> >>    2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
> >>    2 nfs/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 nfs/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
> >> 96-bit SHA-1 HMAC)
> >>    2 nfs/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
> >>    2 nfs/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
> >>
> >> Why do I have duplicate entries in this output? Are they harmful?
> >
> > They represent the different encryption types. They're not harmful but
> > as this is the server, there is no need for the client keys. You can
> > tidy it up using e.g. ktutil.
> >>
> >>
> >> @(nfs|krb) client (hostname "china.mytest.org"):
> >> # klist -ke
> >> Keytab name: FILE:/etc/krb5.keytab
> >> klist: No such file or directory while starting keytab scan
> >>
> >> Client is my problem, how can I get the keys to it? ssh them over?
> >
> > Working on the kdc, create a keytab (as you did above) with the machine
> > key of the client, CHINA$, If you use ktutil, something like:
> > wkt /tmp/china.keytab
> >
> > Then simply copy it to the client using scp or (even easier and more
> > secure) using a USB memory stick. Rename china.keytab to krb5.keytab and
> > copy it 0600 to /etc
> >
> >>
> >> >
> >> > What does /etc/exports look like on the server?
> >>
> >> # cat /etc/exports
> >> /nfsv4krbtest   *(sec=krb5,rw,fsid=0
> >
> > Lose the fsid0. For now, replace the * with the IP of china
> >
> >> # uname -a
> >> Linux test1.mytest.org 2.6.34.10-0.6-desktop #1 SMP PREEMPT 2011-12-13
> >> 18:27:38 +0100 x86_64 x86_64 x86_64 GNU/Linux
> >>
> >> > Note that it is no longer recommended to export nfs4 as a fsid=0 pseudo
> >> > root. Simply export it as we always have done nfs3.
> >>
> >> is this recommendation valid for the quite old 2.6.34.10-0.6-desktop
> >> kernel in Suse 11.3?
> >
> > Dunno. Must it be nfs4 for anything in particular? Security perhaps?
> > nfs3 works fine with kerberos.
> 
> NFSv4 is better for going through a firewall and is less sensitive to
> hacking attempts.
> 
> But:
> if I try to mount the share from the client I now see this:
> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> Mar 19 23:03:43 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:03:43 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:03:43 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> Mar 19 23:03:44 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:03:44 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:03:44 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR:
> prepare_krb5_rfc_cfx_buffer: not implemented
> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR: failed serializing
> krb5 context for kernel
> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
> serialize_context_for_kernel failed
> 
It doesn't like the encryption type. (On openSUSE 13.1 it's been fixed)
Try:
allow_weak_crypto = true
permitted_enctypes = "des-cbc-crc arcfour-hmac des3-cbc-sha1
aes128-cts-hmac-sha1-96 aes256-cts-hmac-sha1-96"

to [libdefaults] in /etc/krb5.conf

> Do you have a very, very bad English curse word which I can use to
> swear at the machine? It doesn't have to be nice or politically
> correct. Just very, very bad.
Yes. Try, 'kerberos'. Shout it very loud as you start rpc.gssd!
> 
> Oh, and I take any suggestions how to fix the 'rpc.svcgssd[5154]:
> ERROR: prepare_krb5_rfc_cfx_buffer: not implemented' too.
Above.
> 

Do you have everything you need?
pa aux | grep rpc
on both server and client
> Wendy
Good luck,
Steve